The effects of short periods of isokinetic resistance training on muscle use and strength were studied. Men (N = 7) trained the right quadriceps femoris muscles nine times over a two-week period using 10 x 5 knee extensions on each occasion.

No changes were found in muscle cross-sectional area, muscle fiber types, fiber area, and phosphofructokinase activity after training. Isometric and isokinetic peak torques across a range of movement velocities and relative area of activated muscle increased significantly.

It was concluded that muscle strength increases after short periods of isokinetic resistance training occurred because of increased contractile activity and not hypertrophy.

Implication. Early strength gains are due to better use of existing resources, not hypertrophied muscle fibers. This supports the notion of there being an initial skill learning response to strength training stimulation, that is, the individual learns to do the activity better.